Known gas discharge-based plasma radiation sources operate at pulse repetition frequencies of <10 kHz, but there are known electrodeless approaches which work at a substantially higher pulse repetition frequency of more than 10 MHz as is disclosed in U.S. Pat. No. 7,605,385 B2. In these methods, the compression of the plasma is implemented through the effect of external magnetic fields and not by a pinch effect which is generated by the current flowing through the plasma.
To achieve the high current strengths of more than 10 kA which are required for a gas discharge-based plasma radiation source, special circuits were developed by which very high outputs (several joules in less than 1 μs) are supplied briefly in the form of pulse-shaped currents and by which, at the same time, disadvantageous effects such as feedback to the technical equipment supplying the pulse-shaped currents can be efficiently reduced. A circuit of this kind is described, for example, in DE 103 61 908 A1.
An apparatus for generating high-energy radiation which works according to the principles described above is described in U.S. Pat. No. 6,566,667 B 1. The apparatus comprises a pulse power source and a vacuum chamber having at least two electrodes between which a buffer gas and a working gas or working gas mixture are injected. The pulse power source has a charging capacitor bank which can be charged in less than 0.5 μs by a charging circuit. Further, devices are provided for controlling the charging process, namely, a magnetic compression circuit having a saturable inductor and at least one charging capacitor bank, a charging bank switch for discharging the latter into the magnetic compression, and a pulse transformer for increasing the pulse voltage by at least a factor of four. The apparatus can be operated without preionization, but appreciably better results with respect to conversion efficiency (ratio of generated radiation output to electric input power) and stability of emission are achieved with preionization.